题目：将学生的学号及平均成绩及格的学生定义成一个视图pjcj ( )
create view pjcj as select stuid,avg(grade) from sc group by stuid having avg(grade)>=60
create view pjcj as select stuid,avg(grade) from sc where avg(grade)>=60 group by stuid
create view pjcj(学号,平均成绩) as select stuid,avg(grade) from sc group by stuid having avg(grade)>=60
create view pjcj(学号,平均成绩) as select stuid,avg(grade) from sc where avg(grade)>=60group by stuid
